CLINICAL LAB SCIENEC

CHAPTER 14: CLINICAL CHEMISTRY 373
after 30 minutes). Plasma obtained by use of a tube with an anticoagulant containing
fluoride is recommended, but any of the common anticoagulants may be used if the
plasma is separated from the blood cells promptly after centrifugation. This procedure
can also be used for the determination of glucose levels in cerebrospinal fluid
(CSF). No special preparation is required unless the CSF sample contains blood;
in such instance, the sample must be centrifuged and removed from the blood, or
glycolysis will occur as it does in blood samples.
Only minimal limitations are incurred when using this procedure where a specific
enzyme reacts with glucose. Both serum and plasma samples are processed in the
same manner, and the samples, when separated from blood cells, are stable for up to
40 hours if stored in a refrigerator at 2°C–8°C. Excessive levels of ascorbic acid are
the chief interfering substance and may result in falsely low glucose values.
Analysis parameters are provided by the manufacturer for procedures using
autoanalyzers as well as for adaptations from these parameters than can be used for
manual procedures. Manual methods may require the same parameters, but some of
them might require manual steps such as manually measuring the samples and timing
them. These tasks might otherwise be handled by automated equipment. These procedures
will be found on package inserts accompanying the test kits and reagents.
Most basic procedures performed in a classroom laboratory, however, will be manual
methods.
The Stanbio enzymatic glucose procedure utilizes a quantitative enzymatic determination
of glucose in plasma, serum, or cerebrospinal fluid.
Equipment and Supplies
1. Gloves, disposable paper towels, and disinfectant or other cleaning solution
2. Report form provided by your instructor
3. Serum, plasma, or other sample
a. Serum sample should be free of hemolysis.
b. Unhemolyzed plasma sample should be from an anticoagulated sample that is
separated from blood cells within 30 minutes of collection.
c. Cerebrospinal fluid sample may be tested by this method.
4. Micropipetter with disposable pipette tips for measuring patient specimen as μLs
5. Serological pipettes
6. Stanbio kit for enzymatic determination of glucose
7. 100 mg/dL standard for calibration; two or three-level control samples depending
upon procedure used to ensure precision
8. Spectrophotometer capable of absorbance readings at 550 nm
9. Water bath or heat block set at 37°C (optional) (The reaction takes 10 minutes at
room temperature, and approximately 3 minutes at 37°C.)
10. Cuvettes
11. 13 × 100 mm test tubes and test tube rack
12. Waterproof sharp marker for labeling test tubes
13. Vortex mixer
14. Electronic timing device or clock/watch with second hand
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